KR102653332B1 - Transition metals doped rhenium selenide nanosheet having enhanced catalytic activity on hydrogen evolution reaction and preparation method thereof - Google Patents

Abstract

The present invention relates to rhenium selenide nanosheets doped with a transition metal having excellent hydrogen evolution reaction (HER) activity and a method of manufacturing the same.

Description

Transition metal doped rhenium selenide nanosheet having enhanced catalytic activity on hydrogen evolution reaction and preparation method thereof}

The present invention relates to rhenium selenide nanosheets doped with a transition metal having excellent hydrogen evolution reaction (HER) activity and a method of manufacturing the same.

In order to overcome serious environmental damage such as resource depletion, global warming, and air pollution caused by the rapidly increasing consumption of fossil fuels, we must find alternative energy sources for the next generation, and this is the biggest challenge that modern humanity must solve. Hydrogen energy burns cleanly in the air and is environmentally friendly. In addition, it is not ubiquitous in the region, making it suitable as the next-generation energy mentioned above. The method of decomposing water using solar energy, which is the most abundant on Earth and produces no pollution, is evaluated as the most environmentally friendly and economical hydrogen production method. The reforming reaction currently mainly used to produce hydrogen has limitations because it uses natural gas or oil, but water is an abundant resource. Therefore, hydrogen production through water decomposition can be said to be the most appropriate method in the long term.

Water electrolysis refers to a reaction in which water is decomposed into hydrogen and oxygen when electricity is applied. In other words, when voltage is applied to the electrode material, an electrochemical redox reaction occurs. At this time, oxygen is generated at the anode and hydrogen is generated at the cathode. The process of decomposing water to produce hydrogen and oxygen is an endothermic reaction due to a large increase in free energy and is an involuntary reaction. Therefore, in order to proceed with the water decomposition reaction, a potential equivalent to 1.23 V must be applied externally, but in reality, depending on the electrode catalyst, more overvoltage than the ideal potential is applied. Water electrolysis is the simplest method to produce hydrogen, and because it uses water as a raw material, it is easy to mass-produce and obtain high-purity hydrogen. However, producing hydrogen through water electrolysis may result in increased power consumption, making it difficult to put into practical use. To this end, the development of a system that increases the efficiency of hydrogen production through water electrolysis and the research on manufacturing technology for electrode catalysts with high activity for hydrogen generation are necessary. The most representative thing that determines performance in water electrolysis is the electrode catalyst, and the phenomenon in which hydrogen is generated through the catalyst is called Hydrogen Evolution Reaction (HER). The required voltage and performance are determined by the electrode material and surface condition. The reversible electrochemical reaction at the electrode surface is as follows.

H ⁺ (aq) + e- → 1/2H ₂ (g), E° = 0V vs. SHE

Based on the hydrogen reduction electrode, hydrogen is generated when the voltage is 0V. When hydrogen is generated on the electrode surface, it occurs through three mechanisms. Basically, hydrogen ions are reduced and adsorbed on the electrode surface in the form of hydrogen atoms (Volmer reaction). Here, it is divided into two paths: hydrogen is generated by combining the adsorbed hydrogen atoms with hydrogen ions in the solution (Heyrowsky reaction) or by combining the adsorbed hydrogen atoms (Tafel reaction). Additionally, Tafel slope is used as a value to identify the mechanism of the hydrogen generation reaction. The equations related to factors affecting hydrogen catalyst activity are as follows.

η = b log( j/j _o )

In the above equation, η: overvoltage, b: Tafel slope, j: current density, j _o : exchange current density. Based on this, an ideal hydrogen catalyst has a low Tafel slope and high exchange current density. has

The factor that has the greatest impact on catalyst activity is overvoltage. Overvoltage is the factor that most significantly contributes to the charge transfer reaction, and the overvoltage value is determined by the speed and whether or not the energy barrier is overcome in catalyst activation. The better the catalyst activation, the lower the overvoltage value. In the case of commercialized platinum electrodes, the voltage when hydrogen is generated is close to 0V. However, hydrogen catalyst research is underway to compensate for the shortcomings of platinum electrodes and minimize overvoltage as much as platinum electrodes. In order to meet the needs of hydrogen catalyst development, it must be a material that has the advantages of low cost and abundance that can compensate for the shortcomings of platinum, and must have good catalytic activity that can replace platinum.

KR 10-1495755 B1

Accordingly, the present inventors made diligent efforts to develop an inexpensive nanomaterial catalyst that can replace platinum (Pt), an expensive noble metal hydrogen generation reaction catalyst, and as a result, transition metal-doped rhenium selenium was obtained using solvothermal synthesis. When manufacturing naked nanosheets, it was confirmed that they had excellent HER performance, and the present invention was completed.

The purpose of the present invention is to provide rhenium selenide nanosheets doped with a transition metal having excellent hydrogen evolution reaction (HER) activity.

Another object of the present invention is to provide a method for producing rhenium selenide nanosheets doped with a transition metal having excellent hydrogen evolution activity.

In order to achieve the above purpose,

This invention

The aim is to provide rhenium selenide nanosheets doped with a transition metal having excellent hydrogen evolution activity.

In the rhenium selenide nanosheet doped with a transition metal according to the present invention, the transition metal is nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), or manganese (Mn), preferably nickel. (Ni) or cobalt (Co), more preferably nickel (Ni).

In the transition metal-doped rhenium selenide nanosheet according to the present invention, the doping concentration of the transition metal is 5% based on rhenium.

In the transition metal doped rhenium selenide nanosheet according to the present invention, the HER performance (10 mAcm ^-2 ) of the transition metal doped rhenium selenide nanosheet is 100 mV or less. For example, the HER performance (10 mAcm ^-2 ) of the transition metal-doped rhenium selenide nanosheet may be 100 mV or less, preferably 90 mV or less, and more preferably 85 mV or less.

In the transition metal-doped rhenium selenide nanosheet according to the present invention, the Tafel slope of the transition metal-doped rhenium selenide nanosheet is 70 mV/dec or less. For example, the Tafel slope of the transition metal-doped rhenium selenide nanosheet may be 70 mV/dec or less, preferably 65 mV/dec or less, and more preferably 60 mV/dec or less.

The present invention also

(A) adding NH ₄ ReO ₄ , (PhCH ₂ ) ₂ Se ₂ , TM (Transition metal) acetylacetonate to oleylamine (C ₁₈ H ₃₅ NH ₂ , OAm) and stirring; and

(B) An excellent hydrogen generation reaction using solvothermal synthesis, which includes the step of subjecting the stirred solution to a solvothermal process to produce rhenium selenide nanosheets doped with a transition metal. The present invention seeks to provide a method for producing rhenium selenide nanosheets doped with an active transition metal.

In the method for producing rhenium selenide nanosheets doped with a transition metal according to the present invention, the transition metal is nickel (Ni), cobalt (Co), iron (Fe), copper (Cu), or manganese (Mn), preferably The following is characterized by nickel (Ni) or cobalt (Co), more preferably nickel (Ni).

In the method for producing a rhenium selenide nanosheet doped with a transition metal according to the present invention, the doping concentration of the transition metal is 5% based on rhenium.

In the method for producing a transition metal doped rhenium selenide nanosheet according to the present invention, the HER performance (10 mAcm ^-2 ) of the transition metal doped rhenium selenide nanosheet is 100 mV or less. For example, the HER performance (10 mAcm ^-2 ) of the transition metal-doped rhenium selenide nanosheet may be 100 mV or less, preferably 90 mV or less, and more preferably 85 mV or less.

In the method for producing a transition metal-doped rhenium selenide nanosheet according to the present invention, the Tafel slope of the transition metal-doped rhenium selenide nanosheet is 70 mV/dec or less. For example, the Tafel slope of the transition metal-doped rhenium selenide nanosheet may be 70 mV/dec or less, preferably 65 mV/dec or less, and more preferably 60 mV/dec or less.

The transition metal-doped rhenium selenide nanosheet according to the present invention has excellent hydrogen generation activity and can provide a catalyst for hydrogen generation reaction in a cheaper and simpler method than a conventional platinum catalyst.

Figure 1(a) shows TM using solvothermal synthesis using NH ₄ ReO ₄ , (PhCH ₂ ) ₂ Se ₂ , TM acetylacetonate (TM (acac)2 or 3), and oleylamine (OAm) as a reagent. -A schematic diagram of the method for synthesizing doped ReSe ₂ is shown. Figure 1(b) shows ReSe ₂ HRTEM image is shown. Figure 1(c) shows the lattice-resolved TEM and corresponding fast Fourier transform (FFT) image for the basal plane. Figure 1(d) shows HAADF-STEM images and EDX elemental mapping/spectra of Re (M shell), Mn or Ni (K shell) and Se (L shell).
Figure 2(a) shows a TEM image of rhenium selenide and transition metal-doped rhenium selenide. Figure 2(b) shows HAADF-STEM images and EDX elemental mapping/spectra of Fe-ReSe _2, Co-ReSe _{2, and} Cu-ReSe ₂ . Figure 2(c) shows rhenium selenide and transition metal doped rhenium selenide. SEM EDX elemental spectrum is shown.
Figure 3(a) shows the representation of rhenium selanide. Represents an atomic-resolution HAADF-STEM image. Figures 3(b), 3(c), 3(d), 3(e), and 3(f) are graphs of Mn, Fe, Co, Ni, and Cu-doped rhenium selenide, respectively. Shows atomic-resolution HAADF-STEM images and electron energy loss spectroscopy (EELS).
Figure 4 shows an X-ray diffraction (XRD) pattern of rhenium selenide and transition metal-doped rhenium selenide.
Figures 5(a), 5(b), and 5(d) show Re 4f, Se 3d, and metal (Mn, Fe, Co, Ni, Cu) of rhenium selenide and transition metal-doped rhenium selenide _2, respectively. ) Shows the Fine-scan results of x-ray photoelectron spectroscopy (XPS) for 2p. Figure 5(c) is the valence band spectrum of rhenium selenide and transition metal doped rhenium selenide. Figure 5(e) is XANES data of rhenium selenide and transition metal doped rhenium selenide. Figure 5(f) is EXAFS data of rhenium selenide and transition metal doped rhenium selenide. Figure 5(g) is EXAFS data of Co K-edge, Ni K-edge, and Cu K-edge of Co, Ni, and Cu doped rhenium selenide.
Figure 6 shows Raman data of rhenium selenide and transition metal doped rhenium selenide.
Figure 7(a) shows transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni) as a catalyst for HER in H ₂ -saturated 0.5 MH ₂ SO ₄ (pH 0). LSV curves (scan rate: 2 mVs ^-1 ) for -ReSe ₂ and Cu-ReSe ₂ ) are shown. Figure 7(b) shows a Tafel plot derived from the LSV curve at low potentials corresponding to the activation-control region using the Tafel equation η=blog(J/J ₀ ), where η is the overpotential and b is the Tafel slope ( mV dec ^-1 ), J represents the measured current density, and J ₀ represents the exchange current density. Figures 7(c) and 7(d) show transition metal doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ ) for HER in H ₂ -saturated 0.5 M KOF (pH 14). , Ni-ReSe ₂ and Cu-ReSe ₂ ), showing LSV curves and Tafel plots, respectively. Figure 7(e) shows η _J=10 (left axis) and Tafel slope (right axis). Figure 7(f) shows TOF at 125 mV. Figure 7(g) shows the LSV curves of Ni-ReSe ₂ for the 1st and 2000th cycles in 0.5 MH ₂ SO ₄ and 1 M KOH and the CA at η _J=10 for 12 hours. Figure 7(h) shows data comparing η _J=10 of Ni-ReSe ₂ with a conventionally known catalyst in 0.5 MH ₂ SO ₄ and 1 M KOH.
Figure 8 shows the results of electrochemical impedance spectroscopy (EIS) analysis of rhenium selenide and transition metal-doped rhenium selenide according to an embodiment of the present invention.
Figure 9 shows the results of Cyclic voltammetry (CV) curve analysis of rhenium selenide and transition metal-doped rhenium selenide according to an embodiment of the present invention. The current density at 0.15 V is plotted according to the scan speed, and the double-layer capacitance (Cdl) value is expressed from the slope.

Hereinafter, the present invention will be described in more detail through examples. However, these are only for explaining the present invention in more detail and the scope of the present invention is not limited thereto.

<Example>

Example 1. Transition metal doped rhenium selenide (TM-ReSe ₂ ) Preparation of nanosheets

Transition metal-doped rhenium selenide (TM-ReSe ₂ where TM is Mn, Fe, Co, Ni, and Cu) nanosheets were prepared using solvothermal synthesis according to the method shown in FIG. 1(a). The doping concentration of five TM-doped ReSe ₂ samples (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) was 5% ([TM]/[Re]=0.05 ) was adjusted.

<Experimental example>

Experimental Example 1. Confirmation of the shape, crystal structure, and electronic structure of rhenium selenide doped with a transition metal according to the present invention.

1-1. HRTEM image analysis

HRTEM (high-resolution transmission) of the transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheets prepared in Example 1 electron microscope) image analysis was performed. As a result, the thickness of the rhenium selenide (ReSe ₂ ) nanosheet was 2 nm on average, and the interlayer distance (d ₀₀₁ ) was 6.5 Å, which was confirmed to be close to the value of 1T″ phase ReSe ₂ (6.3899 Å) (Figure 1(b) )). Average of rhenium selenide (ReSe ₂ ) and transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheets through TEM images It was confirmed that the overall size was similar in the form of a flower of approximately 148 nm (Figure 2(a)).

1-2. Grid-resolution TEM and FFT image analysis of the basal plane

Lattice resolution TEM of the basal surface of the transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ , and Cu-ReSe ₂ ) nanosheet prepared in Example 1 And FFT (fast-Fourier transformed) image analysis was performed. As a result, because the b-beam was projected perpendicular to the basal plane, the FFT image showed a quasi-hexagonal pattern formed by (200), (020), and (220) reflections with the area axis approximately [001]. In fact, the angle γ (between a and b axes) was 118.94°, which was close to the 120° value of the hexagonal unit cell, and the distance ( _d200 ) between adjacent (200) planes was 2.9 Å, which was within the reference value ( It was confirmed to be close to 2.8881 Å) (Figure 1(c)).

1-3. HAADF-STEM and EDX image analysis

_{HAADF - STEM ( high-} Angle annular dark-field imaging-scanning transmission electron microscope) image analysis and EDX (energy-dispersive X-ray spectroscopy) elemental mapping and spectra were measured. As a result, it was confirmed that the transition metal elements Mn, Fe, Co, Cu, Ni, rhenium (Re), and selenium (Se) were uniformly distributed in the transition metal-doped rhenium selenide nanosheet (Figure 1 (d), Figure 2(b)). The SEM EDX elemental spectrum confirmed the presence of approximately 5% of transition metal (Figure 2(c)).

Figure 3 is an atomic-level HAADF-STEM image of the basal plane of rhenium selenide. 1D chains of diamond-shaped Re ₄ clusters connected along the b axis (see red lines) were clearly observed. The lighter Se atoms (Z = 34) are difficult to distinguish in this image. The uniform red color in the contour plot for the marked area of the STEM image represents Re atoms. In contrast, transition metal-doped rhenium selenide had weaker or stronger Re position strengths for TM substitution and adsorption atoms, respectively. Figures 3 (b) and (c) are HAADF-STEM images of Mn-ReSe ₂ and Fe-ReSe ₂ , respectively. Where the intensity of Re is weak, light Mn and Fe atoms (Z = 25 and 26, respectively) are substituted for heavy Re atoms (Z = 75). In the data for the indicated area of the STEM image and the intensity profile along the dotted line, the Re position with weak intensity is a TM atom substituted. The reason that the intensity of the Re position appears brighter is because of the adsorbed atom at that position. EELS data confirmed that Mn and Fe atoms exist as single atoms in the doping site. That is, a spectrum was obtained with a probe size of 1.0 Å, and when the L _2,3 -ionization edge of Mn or Fe was measured, it was confirmed that it exists as an atom at the doped position and does not exist at the atom right next to it. Unlike Mn-ReSe ₂ and Fe-ReSe ₂ , Co-ReSe ₂ and Ni-ReSe ₂ were confirmed to exist as adsorption atoms. The part showing strong intensity in the contour plot is because another adsorbed atom exists at the position of the Re atom. EELS data confirmed that Co and Ni also exist as single atoms. In the case of Cu-ReSe ₂ , it was confirmed that about 2-4 Cu atoms were gathered together like a cluster and were adsorbed and attached. The reason it shows stronger intensity than other metals is because two or more cuppers are clustered together, and EELS data also confirmed that it is clustered more than other metals.

1-4. Confirmation of crystallinity through XRD

Figure 4 shows rhenium selenide (ReSe ₂ ) and transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe) prepared in Example 1. ₂ ) Shows the X-ray diffraction analysis (XRD) results of the nanosheet. Rhenium selenide and transition metal doped rhenium selenide are composed of ReSe ₂ (JCPDS No. 74-0611; a = 6.716 Å, b = 6.728 Å, c = 6.728 Å, and υ = 104.90°) in a 1T″ phase. Confirmed.

1-5. Electronic structure analysis via XPS, XANES, EXAFS

Rhenium selenide (ReSe ₂ ) and transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanostructures prepared in Example 1 For qualitative and quantitative analysis of the catalyst surface of the sheet, Fine-scan XPS (Fine-scan indicated.

As shown in Figures 5(a), 5(b), and 5(d), Re4f _7/2 of rhenium selenide (ReSe ₂ ) peaks at 41.7 eV, which is a higher binding energy than 40.3 eV, which is the value of metal Re. appear. When a transition metal is doped, the peak of Re 4f shifts to red. In the case of Se 3d, like Re 4f, it becomes red-shifted when doped with a transition metal. The valence band maximum (VBM) data is 0.65 eV for rhenium selenide (ReSe ₂ ), but 0.50 eV for Mn and Fe. In the case of Co, Ni, and Cu, the value decreases to 0.36 eV. This is similar to the data of Re 4f and Se 3d. Through the 2p data of the transition metal, it was confirmed that although it was a TM-Se bond, it was almost similar to a metal, and in the case of Cu, it was confirmed that it was in an oxidized state rather than other metals. The red shift of the binding energy may be due to increased conductivity due to the addition of a transition metal doping state at the nearest Fermi level (E _f ). It was confirmed that as it moves from Mn to Cu, the electronic structure of ReSe ₂ becomes more metallic due to the increase in d electrons.

In addition, the results were obtained by analyzing X-ray absorption near edge structure (XANES) analysis and Fourier-transform extended X-ray absorption fine structure (FT EXAFS). is shown in Figure 5(e). Figure 5(e) shows _the . As the transition metal moves from Mn to Cu, the intensity decrease becomes larger, and this is closely related to the red shift of the XPS peak.

In addition, the results were obtained by analyzing X-ray absorption near edge structure (XANES) analysis and Fourier-transform extended X-ray absorption fine structure (FT EXAFS). is shown in Figure 5(f). In the case of ReSe ₂ , through EXAFS data, the shortest bond length among Re-Se bonds is 2.40 Å, and the shortest bond length among Re-Re bonds is 2.84-2.85 Å. From this, it can be confirmed that it is ReSe ₂ on 1T″. The XANES data of the K-edge of the transition metal was Co-Se (2.38 Å) and Ni-Se (2.41 Å), and since there was no bond between Co-Co and Ni-Ni, it was confirmed that they were single atoms. In the case of Cu, Cu-Se and Cu-O bonds were observed.

1-6. Raman analysis

Rhenium selenide (ReSe ₂ ) and transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanostructures prepared in Example 1 Raman analysis was performed on the sheet, and the results are shown in Figure 6. As shown in FIG. 6, the same Raman peak corresponding to 1T″ phase ReSe ₂ is shown. Many peaks arise from the complexity of the lattice vibrations of ReSe ₂ in the 1T″ phase, consistent with previous studies. The peak at 125 cm ^-1 is the Eg-like vibration mode (in-plane vibration), and the peaks at 160 and 174 cm ^-1 are the Ag-like vibration mode (out-of-plane vibration).

Experimental Example 2. Confirmation of electrochemical properties of rhenium selenide doped with transition metal according to the present invention

2-1. Electrochemical experiment method

4 mg of the transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheet sample prepared in Example 1 was mixed with carbon black ( Catalyst ink was prepared by mixing with 1 mg of Vulcan Meanwhile, a Pt/C catalyst material (manufacturer: Sigma-aldrich) containing a standardized 20% by weight nano-sized platinum dispersed in carbon black was purchased and used instead of rhenium selenide nanosheets containing the transition metal. Catalyst ink was prepared in the same manner as above, except that Electrochemical experiments were conducted with a three-electrode cell consisting of a working electrode, a reference electrode, and a counter electrode. Ag/AgCl (4M KCl, manufacturer: Pine Co.) was used as a reference electrode, and a graphite rod (diameter 6 mm) was used as a counter electrode. As a working electrode, 18 ㎕ of the catalyst ink was added dropwise to a glassy carbon electrode (area: 0.1963 cm ² ), which is a rotating disk electrode (RDE), and was dried sufficiently before use.

During the hydrogen evolution reaction (HER) experiment, each was purged with high-purity hydrogen gas, and the gas flow rate was 20 sccm (mL min ^-1 ). The voltage used during measurement was converted based on a reversible hydrogen electrode (RHE).

The reversible hydrogen electrode (RHE) conversion formula at hydrogen ion concentration index (pH) 0 (0.5MH ₂ SO ₄ ) follows the formula below. E (vs. RHE) = E (vs. SCE) + E _SCE (=0.278V) + 0.0592 pH=E(vs.SCE) + 0.278V

The reversible hydrogen electrode (RHE) conversion formula at a hydrogen ion concentration index (pH) of 14 (1M KOH) follows the formula below. E (vs. RHE) =E(vs.Ag/AgCl) + 1.007V

During measurement, the rotating electrode (RDE) was rotated at a speed of 1600 RPM (Revolutions per minute), and the hydrogen evolution reaction (HER) activity was measured through linear sweep voltammetry (LSV).

When measuring using linear scanning potential (LSV), the hydrogen evolution reaction (HER) was measured at a scan rate of 5 mV s ^-1 from 0 V to 0.8 V based on the reversible hydrogen electrode (RHE).

2-2. result

Figure 7(a) shows the LSV curve measured at pH 0, where the potential was based on the reversible hydrogen electrode (RHE). For the overpotential required to obtain a current density of 10 mAcm ^-2 (η _J=10 ), 143 for ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ respectively; They were found to be 132, 115, 104, 82, and 126 mV.

Figure 7(b) shows the Tafel plot, η(V) vs. η(V) in the low potential region. It represents log [J(mAcm ^-2 )]. Tafel slope (b) is 62, 62, 59, 56, 54, 58, and 30 mV for ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ , and Cu-ReSe ₂ , respectively. As dec ^-1 , it was confirmed that HER catalytic activity increased when TM was doped into ReSe ₂ . In particular, Ni-ReSe ₂ was confirmed to have the best catalytic activity among the two-dimensional transition metal chalcogenides doped with the transition metal as η _{J = 10} and b value were close to Pt/C.

Figure 7(c) shows that at pH 14, the LSV curves are 256, 197 for ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ for η _J= 10. , 221, 138, 109, and 179 mV. Tafel plots show corresponding b of 146, 116, 133, 99, 81 and 115 mV dec ^-1 for ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ , respectively. The values are shown (Figure 7(d)) . In particular, the b value of Ni-ReSe ₂ was confirmed to be closest to that of Pt/C (35mV dec ^-1 ).

Figure 7(e) shows η _J=10 and b values, and it was shown that doping ReSe ₂ with Ni maximizes the performance of HER at pH 0 to 14. Overall, the positive effect of TM doping on HER catalytic performance at pH 0 was found to follow the order Ni>Co>Fe>Cu>Mn and at pH 14 it was Ni>Co>Cu>Mn>Fe.

Figure 7(f) plots the TOF values calculated using the LSV curve for each catalyst at 125 mV, and the active surface area is measured based on the CV curve, which ranges from -0.2 to 0.6 V at pH 7. It was estimated. In the case of Ni-ReSe ₂ , the values of TOF (turn of frequency) at pH 1 to 14 were estimated to be 2.5 and 0.91 s ^-1 , respectively.

Figure 7(g) shows that the LSV curve of Ni-ReSe ₂ shows little change at pH 0 to 14 even after 2000 cycles (80 h).

Figure 7(h) compares the catalytic performance of Ni-ReSe ₂ at η _{J = 10} with the conventionally known performance, and it was confirmed to exhibit the best HER catalytic effect.

Figures 8(a) and 8(b) are electrochemical impedance spectroscopy (EIS) data of transition metal-doped ReSe ₂ . A Nyquist plot was made and the real and imaginary resistances were shown while decreasing 0.1 Hz from 100 kHz at -0.15 V as alternating current. By fitting a curve with an electric circuit inserted into the graph, charge transfer resistance (Rct) can be obtained. It can be obtained from the position where the hemispherical curve meets the x-axis, and the smaller it is, the better the catalytic activity. The charge transfer resistance was found to follow the order Ni<Co<Fe<Cu<Mn< _ReSe2 at pH 0 and Ni<Co<Cu<Mn<Fe< _ReSe2 at pH 14.

Figure 9 shows cyclic voltammetry (CV) curve data in the 0.1-0.2 V region. The CV curve was measured as the scan speed increased from 20 mV/s to 100 mV/s. The double-layer capacitance (Cdl) can be obtained from the slope by plotting the current density at 0.15 V according to the scan speed. It was confirmed that at pH 0 it follows the order Ni>Co>Fe>Mn>Cu< _ReSe2 , and at pH 14 it follows the order Ni>Co>Cu>Mn>Fe> _ReSe2 . This can be expected that Ni-ReSe ₂ has the most maximized surface area.

As the specific parts of the present invention have been described in detail above, it is clear to those skilled in the art that these specific techniques are merely preferred embodiments and do not limit the scope of the present invention. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (5)

A rhenium selenide nanosheet doped with a transition metal having hydrogen evolution reaction activity,
The transition metal is nickel (Ni),
The doping concentration of the transition metal is 5% based on rhenium,
The HER performance (10 mAcm ^-2 ) and Tafel slope of the transition metal-doped rhenium selenide nanosheet are respectively 100 mV or less and 70 mV/dec or less. Sheet.
delete A method for producing rhenium selenide nanosheets doped with a transition metal with excellent hydrogen evolution activity using solvothermal synthesis, the method comprising:
(A) adding NH ₄ ReO ₄ , (PhCH ₂ ) ₂ Se ₂ , TM (Transition metal) acetylacetonate to oleylamine (C ₁₈ H ₃₅ NH ₂ , OAm) and stirring; and
(B) subjecting the stirred solution to a solvothermal process to produce rhenium selenide nanosheets doped with a transition metal,
The transition metal is nickel (Ni),
The doping concentration of the transition metal is 5% based on rhenium,
The method is characterized in that the HER performance (10 mAcm ^-2 ) and Tafel slope of the transition metal-doped rhenium selenide nanosheet are 100 mV or less and 70 mV/dec or less, respectively. delete delete